Field of the Invention
The invention relates generally to rotary cutting tools and, more particularly, to rotary cutting tools, such as drills, having polycrystalline-diamond (PCD) cutting tips. The invention further relates to a method for forming a rotary cutting tool having a polycrystalline-diamond cutting tip.
Background Information
Polycrystalline-diamond (PCD) drills have historically been formed as straight fluted, facet point drills. More recently, PCD drills have been formed having helical flutes and more complex point geometries similar to solid carbide drills. One of the major uses of such highly engineered PCD drills is for drilling in composite materials, such as carbon fiber reinforced polymer (CFRP) titanium composites. Drills used for cutting such material require a high wear resistance to survive in CFRP while having a geometry that is effective to cut titanium. Aerospace customers, who commonly utilize such CFRP composite materials, further require that the burr height of the titanium portion of the drilled composite material be maintained around 100 microns. Known PCD drills produce a high quality hole in the first few holes, but rapidly begin to produce unacceptable burrs soon thereafter (typically about 5 holes or less). Accordingly, such drills must be replaced frequently at a high cost.
There is, therefore, room for improvement in rotary cutting tools used for drilling CFRP-titanium, particularly in the quality of the holes cut and the durability of the cutting tool.